Aerosol therapy is commonly prescribed for patients suffering from various respiratory ailments, such as asthma, emphysema and pnemonia. It is also a common post-operative treatment following throat surgery and for patients receiving oxygen treatment, which tends to dry out membranes. In a common aerosol therapy system a mixture of oxygen and air with water in a very fine particulate form suspended therein is discharged into a face tent which fits snugly around the cheeks and chin of the patient but is open at the top to allow free flow of aerosolized fluid therefrom. At relatively high flow rates, e.g. 30 to 40 liters of oxygen-air mixture per minute, the unrestrained aerosol fluid flows freely out of the face mask without being retained long enough to enable the patient to inhale an appreciable amount thereof. Others have attempted to slow the flow rate by applying check valves or the like, but such commonly results in a build up of back pressure. Since the ratio of air to pure oxygen is determined by the air intake opening on the jet nebulizer, as well as the flow rate of the oxygen, and increase in back pressure will back up to the air intakes to block them, thereby increasing the oxygen concentration.